Polymer blending is a method to achieve new materials with different properties. Polycarbonate (PC) is a commonly used engineering thermoplastic polymer because of its good impact strength, transparency and electrical properties. However, PC is inferior to many other transparent resins in scratch resistance. In contrast, polymethyl methacrylate (PMMA) has excellent scratch resistance. Blending polycarbonate with PMMA has been studied with the intention of combining the properties of these two polymers—particularly enhanced scratch resistance.
Creating blends of PMMA and PC, however, is problematic. It is known that melt blends of PC and PMMA are immiscible resulting in an opaque blend rather than a transparent blend needed for certain uses such as optical applications. The opaqueness is believed to be due to differences in the refractive index difference between PC and PMMA and the lack of compatibility. Compatibilization is needed to decrease the size of the dispersed phase and achieve a transparent blend. Different strategies have been adopted to produce less opaque PC/PMMA blends. Efforts have focuses on high shear mixing to produce smaller polymer domains (U.S. Pat. No. 8,440,760), modification of the PC and/or PMMA polymers WO 2012/037461), and grafting PMMA side chains to PC (Okamoto, J. Appl. Polym. Sci. 2001, 80, 2670-2675). To date, these efforts have failed to produce a transparent blend. There is a need in the art for transparent polymers that overcome the above deficiencies.